Irish Journal of Earth Sciences最新文献

{"title":"A Silurian (Llandovery) Eoplectodonta Shell Bed in Western Ireland: The Role of Opportunism, Storms and Sedimentation Rates in Its Formation","authors":"D. Harper, Eamon Doyle","doi":"10.3318/IJES.2003.21.1.105","DOIUrl":"https://doi.org/10.3318/IJES.2003.21.1.105","url":null,"abstract":"Abstract:The ambitopic brachiopod Eoplectodonta is common in many upper Llandovery assemblages from deep-water settings, but this small plectambonitoid is not a noted opportunist. At least one level within the Telychian Kilbride Formation of north Connemara, western Ireland, contains unusual shelly associations overwhelmingly dominated by Eoplectodonta penkillensis (Reed). An opportunist model is developed for this assemblage based on the availability of vacant soft substrates periodically created after intermittent storm activity on the deep shelf. In addition, rapid sediment accumulation during transgression may have been an important contributing factor in this high-stress environment.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"21 1","pages":"105 - 114"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48098356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Locating the Shannawona Fault: Field and Geobarometric Studies from the Galway Batholith, Western Ireland","authors":"B. Callaghan","doi":"10.3318/IJES.2005.23.1.85","DOIUrl":"https://doi.org/10.3318/IJES.2005.23.1.85","url":null,"abstract":"Abstract:The Shannawona Fault Zone is a critical region of the Galway Batholith, juxtaposing deep-level Central Block lithologies against shallower-level granites of the Western Block. This paper presents results of the first detailed field mapping of the Shannawona Fault Zone between Casla Bay and Lackadunna Hill. Here the Shannawona Fault is not a discrete structure, but bifurcates and conjoins repeatedly to form an anastomosing fault system. Minor fault-bounded blocks defined by this fault system are lithologically associated with the Western Block New geobarometric studies undertaken in the area reveal a contrast of >1kbar in crystallisation pressures across the main Shannawona Fault, as identified from the field mapping Geobarometry indicates that the minor fault-bounded blocks originated at depths similar to the Western Block.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"23 1","pages":"100 - 85"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48059747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sm-Nd Mineral Ages and P-T Constraints on the Pre-Grampian High Grade Metamorphism of the Slishwood Division, Northwest Ireland","authors":"M. Flowerdew, J. Daly","doi":"10.3318/IJES.2005.23.1.107","DOIUrl":"https://doi.org/10.3318/IJES.2005.23.1.107","url":null,"abstract":"Abstract:Granulite-facies metamorphism affecting the Slishwood Division was extreme. Three samples yielded P-T conditions of 15.8, 14, 14.9kbar at 810, 750 and 880°C, respectively. Four Sm-Nd mineral isochrons, defined by granulite-facies basic and pelitic metamorphic assemblages, yield ages of 544 ± 52 Ma, 539 ± 11 Ma, 596 ± 68 Ma and 540 ± 50 Ma. These ages confirm that granulite- and earlier eclogitefacies metamorphism took place before the c. 470Ma Grampian Orogeny. Detailed chronological interpretation is inhibited by microscopic inclusions within, and isotope disequillbnum between, the dated minerals It is possible that the ages record crystallisation of either the granulite or eclogite-facies assemblages. However, it is more likely that they record post-metamorphic cooling. Relict pre-granulite-facies igneous minerals from a metagabbro body possibly date its intrusion at 580 ± 36 Ma. Extreme metamorphism in the late Neoproterozoic to Early Cambrian suggests that the Slishwood Division is exotic to Laurentia.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"23 1","pages":"107 - 123"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44533253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE LAST GLACIATION OF ARAN ISLAND AND CRUIT ISLAND, CO. DONEGAL, NORTH-WEST IRELAND","authors":"J. Knight","doi":"10.3318/IJES.2012.30.49","DOIUrl":"https://doi.org/10.3318/IJES.2012.30.49","url":null,"abstract":"Abstract:This paper describes geomorphological and sedimentary evidence from Aran Island and Cruit Island (County Donegal, north-west Ireland), informed by evidence from across west Donegal, which helps to show the processes of ice advance and retreat and subglacial conditions during the last (late Midlandian) glaciation. Extensive abraded rock surfaces show clear evidence for ice overtopping of the islands. Erosional landforms include striae, flutes developed in bedrock, whalebacks, roches mountonnées and meltwater channels. Depositional landforms include erratic boulders and a single marginal moraine on Aran Island. Glacial or glacially-influenced sediment deposition that does not have a geomorphic expression took place into bedrock hollows during an ice advance stage, probably around the time of the last glacial maximum. The dominance of erosional signatures likely reflects the stripping by ice of a surficial cover of weathered pre-glacial granite debris. The general absence of subglacial and ice-marginal sediments across the region likely reflects the granite substrate and coarse granitic weathering products, which did not favour development of a thick deformable sediment pile.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"30 1","pages":"49 - 58"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43347869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining Sinistral Shearing in NW Ireland: A Precise U-Pb Zircon Crystallisation Age for the Ox Mountains Granodiorite","authors":"D. Chew, U. Schaltegger","doi":"10.3318/IJES.2005.23.1.55","DOIUrl":"https://doi.org/10.3318/IJES.2005.23.1.55","url":null,"abstract":"Abstract:The age of the Ox Mountains Granodiorite has proved controversial in the past. Two published Rb-Sr whole rock isochrons suggest ages of $487 pm 6 Ma$ and 500 $pm 18 Ma$, respectively ($lambda^{87}Rb = 0.0139 Ga^{-1}$), whereas Rb-Sr muscovite-feldspar isochrons from undeformed pegmatites associated with the intrusion have yielded c. 400Ma ages. The syn-kinematic nature of the Ox Mountains Granodiorite has been clearly demonstrated by several workers, with the pluton being emplaced as a series of sheets in a major transpressive sinistral shear zone. Knowledge of the age of crystallisation of the Ox Mountains Granodiorite would thus constrain the timing of strike-slip movement along this shear zone, which forms part of a major Caledonide structure known as the Fair Head - Clew Bay Line. A U-Pb zircon age (conventional isotope dilution TIMS) of $412.3 pm 0.8 Ma$ from a tonalitic facies of the pluton is presented here. The age confirms that emplacement was broadly contemporaneous with the majority of other volumetrically important Irish granite batholiths (i.e. Leinster, Donegal, Galway and Newry), while $inHf_{(412)}$ values of the dated zircons (which range from -5.4 to -7.7) imply incorporation of old crustal material into the parent melt.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"23 1","pages":"55 - 63"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48325798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"REPLY TO KNIGHT","authors":"D. M. Williams","doi":"10.1353/ijes.2011.0003","DOIUrl":"https://doi.org/10.1353/ijes.2011.0003","url":null,"abstract":"","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"29 1","pages":"25 - 26"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48512831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stable Isotope Evidence for Diagenesis of the Ordovician Courtown and Tramore Limestones, South-Eastern Ireland","authors":"M. Key, P. N. Wyse Jackson, W. Patterson, M. D. Moore","doi":"10.3318/IJES.2005.23.1.25","DOIUrl":"https://doi.org/10.3318/IJES.2005.23.1.25","url":null,"abstract":"Abstract:Use of Lower Palaeozoic carbonate fossils for palaeothermometry as derived from stable isotope geochemistry is increasing. With all these studies, there is the concern of how pristine the skeletal carbonate is in relation to diagenesis. In this study, we compared the stable isotopes of calcitic brachiopod and bryozoan allochems with secondary cements to determine if the skeletal isotopes were reset during diagenesis. The study was conducted on the Courtown and Tramore Limestone Formations of the Ordovician (Llanvirn-Caradoc) Duncannon Group, which outcrops in south-eastern Ireland. These formations consist of calcareous mudrocks and argillaceous limestones. Bryozoans and brachiopods are common allochems in both formations. The Duncannon sediments were cleaved, folded and faulted by compression associated with the Caledonian and Hercynian orogenies. Bulk rock samples were slabbed and thick-sectioned. Fifty three $geq20mu$g samples of carbonate from bryozoans, brachiopods and matrix (cements and veins) were collected with 1μm spatial precision using a computer-driven micromilling device to minimise mixing of allochems and matrix. Results indicate $delta^{13}C$ values of -8.8% to +0.3% VPDB and $delta^{18}C$ values of -17.8% to -11.5% VPDB. In the Courtown samples, the brachiopod and bryozoan $delta^{18}C$values were consistently more similar to each other than either was to the matrix, but this was not true for the Tramore samples. This suggests different alteration histories (more likely) or a different source of carbonate for the Courtown matrix (i.e. sparry cement) as opposed to that of the Tramore matrix (i.e. abraded skeletal material) (the less likely explanation). Palaeotemperature calculations from the oxygen isotopes ($78degreeC to 128degreeC$) indicate exposure to isotopically light groundwater or meteoric fluids following the previous and hotter Caledonian and Hercynian orogenies. All three phases of alteration would have overprinted any original palaeoenvironmental signal that might once have existed.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"23 1","pages":"25 - 38"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48778331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic survey sound propagation: a Porcupine Basin noise-field","authors":"Eoghan Daly, S. Jordan, M. White","doi":"10.3318/ijes.2020.38.4","DOIUrl":"https://doi.org/10.3318/ijes.2020.38.4","url":null,"abstract":"Abstract:Anthropogenic noise in the ocean's water column, including from offshore seismic surveys, is ever increasing, bringing greater ecological pressure on the marine environment and with that a need to measure, understand and mitigate against these sources of noise pollution. Here, a previous study on an offshore seismic survey along the Irish continental margin is utilised to gain further insight into sound propagation in this sensitive area for marine mammals. Propagation pathways, along with seasonal variability and modelled slope conditions are investigated to constrain sound levels relative to those that can cause harm. Results are discussed in the context of noise pollution in the Porcupine Basin (e.g. geoacoustic and environmental parameters, including slope angle, topography, seasonality and the water column). Acoustic model functionality is assessed. Noise exposure criteria and behavioural disturbance to marine mammals are considered alongside regulatory frameworks, with the future aim of increasing Ireland's capacity to limit the effects of ocean noise pollution.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"38 1","pages":"25 - 39"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48793274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Connemara Eastern Boundary Fault: A review and assessment using new evidence","authors":"A. Lees, M. Feely","doi":"10.3318/IJES.2016.34.1","DOIUrl":"https://doi.org/10.3318/IJES.2016.34.1","url":null,"abstract":"Abstract:The boundary between the Carboniferous sedimentary rocks and the igneous and metamorphic rocks of the Connemara basement between Galway and Oughterard has been described, either all or in part, as an unconformity or a fault known as the Oughterard Fault. We present new data on the geology of this boundary. A significant faulted contact in the Moycullen area is described for the first time and integrated with other new and existing data to form a reassessment of the nature of the boundary. Arguments for the presence of a fault or unconformity are posited. It is concluded that the whole length of the boundary is faulted. Finally, an exploration of possible extensions to the boundary fault is presented. It is suggested that the fault zone could extend southwards into the Gort Lowlands, and, at the northern end, it may be linked to the Maam Valley Faults.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"34 1","pages":"1 - 25"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3318/IJES.2016.34.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42117203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Earth science conservation in Ireland—a reappraisal","authors":"Sarah Gatley, M. Parkes","doi":"10.3318/IJES.2016.34.79","DOIUrl":"https://doi.org/10.3318/IJES.2016.34.79","url":null,"abstract":"Abstract:This paper assesses how geoconservation efforts in Ireland have proceeded since 2001 when a road map of intended actions was laid out. The plan to roll out a national network of geological Natural Heritage Areas (NHAs) has been augmented by a further initiative, largely driven by availability of financial resources and a demand for geological heritage data during booming economic times. Rather than focusing on NHAs, the primary effort of the Irish Geological Heritage Programme of Geological Survey Ireland is now aimed at achieving full national coverage of audited County Geological Sites (CGSs) in Ireland by 2022. CGSs can have much more local or national importance and still be geological NHAs in future. CGSs have no statutory protection, but receive effective protection through inclusion in the statutory County Development Plan of each local authority. The focus on CGSs also allows an expanded vision of what may be encompassed, such as mining heritage, urban sites and new road cuttings, as well as public amenity sites incorporating geology and educational sites. The important role of Geoparks in raising awareness of geoconservation is also reviewed.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"34 1","pages":"79 - 89"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41556931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}